Humans are constantly confronted with the need to choose an optimal course of action given different expectations about rewards. The neural mechanisms by which information about rewards is incorporated into ongoing decisions about what action to take remain poorly understood, despite the fact that their disruption is closely associated with several debilitating disorders, including depression and addiction. I propose to directly investigate how rewards are integrated with ongoing decisions by both recording and manipulating the posterior cingulate cortex, a cortical region that is likely to play a critical role in this process. In one study, I will determine which of two possible economic variables is represented by PCC neurons by recording responses of single neurons while subjects perform a task that dissociates subjective expected utility from risk. In a second study, I will investigate what aspects of risky decision-making are subserved by PCC neurons by examining the effect of microstimulation on choice behavior in the visual gambling task. In a third study, I will investigate whether PCC integrates information about recent wins and losses in gambles to guide current decisions by examining how reversibly inactivating PCC affects how subjects respond to different gamble outcomes. Together, these studies will significantly advance our understanding of the role of PCC in reward-guided decision-making. Failures of the network of the brain responsible for using information to make rewards to make decisions cause many mental disorders, including depression, anxiety, obsessive compulsive disorder, and addiction. This project will investigate how healthy brains perform this task by recording and altering the responses in a brain region that plays a central role in these processes. [unreadable] [unreadable] [unreadable]